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No RAID
For
those who are having a dual (triple or quad) boot system in your
computer, chances are, your bootloader might break when you update one
OS to a newer version. If you are using Ubuntu (with the new Grub 2
bootloader) and you installed Windows. The Windows bootloader will erase
your Grub 2 and you won’t be able to boot in your Ubuntu. As such, you
will need to restore your bootloader to Grub 2.Note: If you are still using the Grub legacy, check out this post to restore your Grub.Requirement: Ubuntu (Karmic or Lucid) LiveCD (download it from Ubuntu.com) Start your computer and boot into your Ubuntu LiveCD.
The
first thing that we need to do is to mount your existing Ubuntu
partition. If you already know your partition number (of the form sda1, sdb2 etc), you can easily mount using the following command:

sudomount/dev/sda1 /mnt #replace sda1 with your partition number

If however, you have completely no idea of your partition number, launch GParted (System -> Administration -> gParted). Locate your Ubuntu partition and record down the partition number.
If you are are using different partitions for the root and the home folder, make sure you record the root partition instead of the home.
Close the GParted. Open a terminal and type in the following command:

sudomount/dev/sda1 /mnt #replace sda1 with your root partition number

Next, all you need to do is to reinstall Grub 2 with the following command: